Floaters, officially called entoptic phenomena are the normal appearance of asymmetrical, drifting images that appear to occur inside the eye itself. Several causes may include shadows of cells or coagulated proteins in front of the retina. They are more common when focusing on a bright background, such as the sky or a computer screen, or having a bright light shone into the eyes, such as during an optical exam.
A sudden increase of floaters could indicate retinal detachment, i.e., a detachment of the lining of the back of the eye, which would require immediate medical attention.
The prevalence of spots, floaters, halos, +/or flashes in a chronic fatigue syndrome cohort was 20.6% in a 2001 report for CFIDS Association of America, Visual Dysfunction in Chronic Fatigue Syndrome by Lesley J. Vedelago, OD.